RX and RXI® for Optical Wireless Communications
Ultra compact optics for optical wireless communications Juan C. Miñano, Pablo Benítez, Rubén Mohedano, José L. Alvarez, Maikel Hernández, Juan C. González*, Kazutoshi Hirohashi**, Satoru Toguchi** IES, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid, 28040 Madrid, Spain *Universidad Europea de Madrid, Villaviciosa de Odón, Madrid, Spain **HITS (High Speed Infrared Transmission Systems) Laboratories, Inc., 2-16-16 Chuourinkan, Yamato, 242-0007 Japan ABSTRACT Advanced optical design methods [J.C. Miñano, J.C. González, “New method of design of nonimaging concentrators”, Appl. Opt. 31, 1992, pp.3051-3060] using the keys of nonimaging optics lead to some ultra compact designs which combine the concentrating (or collimating) capabilities of conventional long focal length systems with a high collection efficiency [J.C. Miñano, J.C. González, P. Benítez, “A high gain, compact, nonimaging concentrator: the RXI”, Appl. Opt. 34, 1995, pp. 7850-7856 ][ J.C. Miñano, P. Benítez, J.C. González, “RX: a nonimaging concentrator”, Appl. Opt. 34, 1995, pp. 2226- 2235]. One of those designs is the so-called RXI. Its aspect ratio (thickness/aperture diameter) is less than 1/3. Used as a receiver, i.e. placing a photodiode at the proper position, it gets an irradiance concentration of the 95% of the theoretical thermodynamic limit (this means for example, a concentration of 1600 times with an acceptance angle of ±2.14 degrees). When used as an emitter (replacing the aforementioned photodiode by an LED, for instance), similar intensity gains may be obtained within an angle cone almost as wide as the 95% of the thermodynamic limit. In a real device these irradiance (and intensity) gains are reduced by the optical efficiency.
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